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United States Patent |
6,250,747
|
Hauck
|
June 26, 2001
|
Print cartridge with improved back-pressure regulation
Abstract
A print cartridge is used in a printing system in which there is a
requirement to provide two distinct rates of ink usage corresponding to
two different types of printing done with the printing system. The print
cartridge includes an ink replenishment path which selectively provides
two flow rates into the print cartridge. The print cartridge also includes
a controller which selects one of the two flow rates into the print
cartridge based on which type of printing is being performed by the
printing system.
Inventors:
|
Hauck; Mark (Corvallis, OR)
|
Assignee:
|
Hewlett-Packard Company (Palo Alto, CA)
|
Appl. No.:
|
239504 |
Filed:
|
January 28, 1999 |
Current U.S. Class: |
347/86 |
Intern'l Class: |
B41J 002/175 |
Field of Search: |
347/84,85,86,87,89
|
References Cited
U.S. Patent Documents
5220345 | Jun., 1993 | Hirosawa | 347/17.
|
5719609 | Feb., 1998 | Hauck et al. | 347/85.
|
5880748 | Mar., 1999 | Childers et al. | 347/6.
|
5923353 | Jul., 1999 | Boyd et al. | 347/85.
|
5992990 | Nov., 1999 | Childers et al. | 347/87.
|
6039442 | Mar., 2000 | Hagiwara et al. | 347/89.
|
Other References
Patent Application: Serial Number: 08/718,615; "A Fail-Safe, Backup Valve
In A Pressurized Ink Delivery Apparatus"; Boyd et al.; filed Sep. 23,
1996.
|
Primary Examiner: Le; N.
Assistant Examiner: Nghiem; Michael
Attorney, Agent or Firm: Myers; Timothy F.
Claims
What is claimed is:
1. A print cartridge for use in a printing system, the print cartridge
having at least two distinct rates of ink usage corresponding to at least
two types of printing performed by the printing system, the print
cartridge comprising:
an ink replenishment path for selectively providing at least two flow rates
in stages into the print cartridge; and
a controller for sensing gauge pressure and in response selecting a
particular flow rate from the at least two flow rates based on the type of
printing being performed by the printing system.
2. The print cartridge of claim 1, further comprising:
a removal path operated by the controller in response to gauge pressure
within the print cartridge, the removal path for extracting excess air and
ink from within the print cartridge to regulate the gauge pressure to a
predetermined range suitable for the particular types of printing
performed by the printing system.
3. The print cartridge of claim 2 wherein said fluid source is integral to
the print cartridge.
4. The print cartridge of claim 3, wherein said fluid source further
comprises a source inlet wherein said fluid source is capable of being
replenished with a quantity of fluid through said source inlet.
5. The print cartridge of claim 3, wherein said fluid source further
comprises a source inlet wherein said fluid source is capable of being
pressurized though said source inlet.
6. A media printing apparatus comprising at least one print cartridge of
claim 1.
7. A print cartridge for selectively depositing fluid on media, the print
cartridge having a reservoir containing a quantity of fluid, the print
cartridge comprising:
a first valve defining a first fluid path between a fluid source and the
reservoir;
a second valve defining a second fluid path, different from the first fluid
path, between the fluid source and the reservoir;
a controller linked to each of said first and said second valves; and
wherein said controller is responsive to gauge pressure in said reservoir
for selectively modulating each of said first and said second valves to
provide a staged fluid flow from the first and the second fluid paths,
respectively, into the reservoir.
8. The print cartridge of claim 7, further comprising:
an inlet; and
a third valve disposed in a third path between said inlet and the
reservoir;
wherein said controller is further responsive to gauge pressure in said
reservoir for selectively modulating said third regulator to provide
additional staged fluid flow from the third path into the reservoir.
9. The print cartridge of claim 8, wherein said inlet is coupled to a
vacuum.
10. The print cartridge of claim 9, further comprising a second reservoir
containing said vacuum, wherein the second reservoir is disposed between
said inlet and said third valve.
11. The print cartridge of claim 10, wherein said second reservoir is
capable of being removed and replaced on the print cartridge.
12. The print cartridge of claim 9, wherein said controller is responsive
to gauge pressure in the reservoir for modulating said third valve to
evacuate air from the reservoir.
13. The print cartridge of claim 7 wherein said fluid source is capable of
being removed and replaced on the print cartridge.
14. A print cartridge for selectively depositing fluid on media, the print
cartridge having a first inlet and a reservoir containing a quantity of
fluid, the print cartridge comprising:
a first regulator, disposed in a first path between the first inlet and the
reservoir;
a second inlet;
a second regulator disposed in a second path between said second inlet and
the reservoir; and
a controller linked to said first regulator and said second regulator;
wherein the reservoir is capable of having a pressure sensed by said
controller, and wherein said controller is capable of selectively
modulating said first regulator and said second regulator to provide
adjustment of the pressure in the reservoir.
15. The print cartridge of claim 14, further comprising a third regulator,
disposed in a third path between the first inlet and the reservoir wherein
said first path is distinct from said third path and wherein said
controller is capable of selectively modulating said first regulator and
said second regulator to provide multiple levels of fluid flow into said
reservoir in response to the pressure sensed by said controller.
16. The print cartridge of claim 14, wherein said second inlet is coupled
to a vacuum.
17. The print cartridge of claim 16, further comprising a second reservoir
containing said vacuum, wherein said second reservoir is disposed between
said second inlet and said second regulator.
18. The print cartridge of claim 17, wherein said second reservoir is
capable of being removed and replaced on the print cartridge.
19. The print cartridge of claim 16, wherein said controller is capable of
modulating said second regulator to evacuate air from the reservoir.
20. The print cartridge of claim 14, further comprising:
a fluid source capable of being fluidically coupled to said first inlet,
and
wherein said fluid source is capable of being removed and replaced on the
print cartridge.
21. The print cartridge of claim 14, further comprising:
a fluid source fluidically coupled to said first inlet; and
wherein said fluid source is integral to the print cartridge.
22. The print cartridge of claim 21, wherein said fluid source further
comprises a source inlet wherein said fluid source is capable of being
replenished with a quantity of fluid through said source inlet.
23. The print cartridge of claim 21, wherein said fluid source further
comprises a source inlet wherein said fluid source is capable of being
pressurized though said source inlet.
24. A printing apparatus comprising at least one print cartridge of claim
14.
25. An apparatus for maintaining pressure regulation in a reservoir
containing a quantity of fluid, the apparatus comprising:
a first valve having an input and an output coupled to the reservoir;
at least one additional valve having an input and an output coupled to the
reservoir; and
a controller capable of selectively modulating the first valve and the at
least one additional valve based on the gauge pressure in the reservoir;
wherein the valve and the at least one additional valve are capable of
providing multiple levels of fluid flows into the reservoir.
26. The apparatus of claim 25, further comprising an third valve having an
input and an output coupled to the reservoir, said third valve capable of
being modulated by said controller based on the gauge pressure in the
reservoir, wherein said third valve is capable of evacuating air from the
reservoir.
27. A print cartridge comprising the apparatus of claim 26, the print
cartridge further comprising:
a vacuum source coupled to the input of the third valve;
a fluid source coupled to the input of the first valve and the input of the
at least one additional valve; and
a printhead capable of reducing the gauge pressure in the reservoir by
ejecting portions of the quantity of fluid;
wherein the apparatus is capable of counteracting the reduction of gauge
pressure.
28. A print cartridge comprising the apparatus of claim 25, the print
cartridge further comprising:
a fluid source coupled to the input of the first valve and the input of the
at least one additional valve; and
a printhead capable of reducing the gauge pressure in the reservoir by
ejecting portions of the quantity of fluid;
wherein the apparatus is capable of counteracting the reduction of gauge
pressure.
29. An apparatus for maintaining pressure regulation in a reservoir
containing a quantity of fluid under pressure, the apparatus comprising:
a first regulator capable of modulating a first fluid flow into the
reservoir;
a second regulator capable of modulating a second fluid flow into the
reservoir, the first fluid flow distinct from the second fluid flow; and
a controller capable of selectively modulating the first regulator and the
second regulator based on the gauge pressure in the reservoir;
wherein the first fluid flow and the second fluid flow are capable of
providing multiple levels of fluid flow into the reservoir.
30. A print cartridge comprising the apparatus of claim 29, the print
cartridge further comprising:
a fluid source coupled to the first regulator and the second regulator; and
a printhead capable of reducing the gauge pressure in the reservoir by
ejecting portions of the quantity of fluid;
wherein the apparatus is capable of counteracting the reduction of gauge
pressure.
31. An apparatus for maintaining pressure regulation in a reservoir
containing a quantity of fluid under pressure, the apparatus comprising:
a first regulator capable of modulating a fluid flow into the reservoir;
a second regulator capable of modulating an air flow from the reservoir;
and
a controller capable of selectively modulating the first regulator and the
second regulator based on the gauge pressure in the reservoir;
wherein the second regulator is capable of evacuating air from the
reservoir.
32. The apparatus of claim 31, further comprising a third regulator capable
of modulating a second fluid flow into the reservoir, the second fluid
flow distinct from the first fluid flow and wherein the controller further
is capable of selectively modulating the second fluid flow based on the
gauge pressure in the reservoir wherein the first fluid flow and the
second fluid flow are capable of providing multiple levels of fluid flow
into the reservoir.
33. A print cartridge comprising the apparatus of claim 32, the print
cartridge further comprising:
a vacuum source coupled to the second regulator;
a fluid source coupled to first regulator and the third regulator; and
a printhead capable of reducing the gauge pressure in the reservoir by
ejecting portions of the quantity of fluid;
wherein the apparatus is capable of counteracting the reduction of gauge
pressure.
34. A print cartridge comprising the apparatus of claim 31, the print
cartridge further comprising:
a vacuum source coupled to the second regulator;
a fluid source coupled to first regulator; and
a printhead capable of reducing the gauge pressure in the reservoir by
ejecting portions of the quantity of fluid;
wherein the apparatus is capable of counteracting the reduction of gauge
pressure.
Description
FIELD OF THE INVENTION
The present invention generally relates to ink-jet printing, and more
particularly, to apparatus and methods for delivering fluid to printheads
while maintaining control of back-pressure within the printhead.
BACKGROUND OF THE INVENTION
The art of inkjet technology is relatively well-developed. Commercial
products of recording or printing apparatus such as computer printers,
graphics plotters, and facsimile machines employ inkjet technology for
producing recorded media. Hewlett-Packard's contributions to this
technology, ink-jet in particular, are described in various articles in
the Hewlett-Packard Journal, Vol. 36, No. 5 (May 1985), Vol. 39, No. 4
(August 1988), Vol. 39, No. 5 (October 1988), Vol. 43, No. 4 (August
1992), Vol. 43, No. 6 (December 1992), and Vol. 45, No. 1 (February 1994).
A ink-jet image is formed when drops are ejected from a drop-generating
device known as a "printhead" to form precise patterns on a recording
medium such as paper, vellum, or acrylic slide material to name a few. The
drop-generating device uses any suitable technology for selectively
depositing ink on media such as thermal ink-jet or piezo to name a couple.
In the case of thermal ink jet, a typical ink-jet printhead has an array
of precisely formed nozzles attached to a thermal ink-jet printhead
substrate. This substrate incorporates an array of ink ejection chambers
that receive liquid fluid, such as ink, from a fluid reservoir in a print
cartridge containing the printhead. Each ink ejection chamber in the
printhead has a thin-film resistor, known as a "firing resistor," located
opposite each nozzle so fluid can collect between the firing resistor and
the nozzle. When the firing resistor is selectively activated, a small
volume of fluid adjacent the firing resistor is heated, vaporizing a
bubble of fluid, and thereby ejecting a drop of fluid from the printhead.
The droplets strike the recording medium and then dry to form "dots" that,
when viewed together, form the recorded image.
In general, the fluid in the fluid reservoir within the print cartridge has
an operating pressure chosen with at least two limiting conditions. First,
the operating pressure must be sufficiently negative, creating a
"back-pressure", so that during printhead operation fluid does not run
freely through the ink ejection chambers and exit from the nozzles. This
phenomenon of free running fluid is called "drooling". Secondly, the
operating pressure of the printhead must not be too negative so that when
the firing resistor is heated, the vaporized bubble of fluid can overcome
this operating back-pressure and eject a droplet of fluid from the ink
ejection chamber. Most printheads today operate in a slight vacuum,
typically in a gauge pressure range of between about -2 inches (minus two
inches) of water to about -10 inches (minus ten inches) of water. Gauge
pressure is pressure measured relative to atmospheric pressure outside of
the print cartridge. Atmospheric pressure outside of the print cartridge
is defined as 0 (zero) inches of water.
Some ink-jet printheads are located in printers or other media-recording
apparatus having pressurized fluid supplies. Pressurized fluid systems
enable fluid to be supplied to the printhead at higher fluid flow rates
than non-pressurized systems, thus allowing for greater reliability and
high print rate printing for applications such as large format or high
density printing. The fluid in typical pressurized systems is pressurized
from a fluid source to a supply pressure of between about +30 inches (plus
thirty inches) of water to about +3 inches and is delivered to the
printhead using either a tube or a conduit. A back-pressure regulator is
normally located near the printhead, such as in a print cartridge
containing the printhead, to reduce the supply pressure of the fluid down
to the operating pressure required of the printhead.
Consumers, particularly of digital photography, are demanding fast printing
speeds and photographic film quality results. To meet these consumer
demands, as well as others, requires substantially increasing the rate of
fluid ejected from the printhead. Another problem encountered when
printing photographs onto recording medium at high speed is that the fluid
leaving the printhead causes the back-pressure within the reservoir of the
print cartridge to change, sometimes abruptly. Consistent drop volume for
the fluid ejected is required for photographic quality, however, the drop
volume is affected by the changing back-pressure. Printing at these high
use rates requires that the regulator have a faster response time than
required with low use rates to maintain adequate back-pressure regulation.
If the back-pressure regulator cannot provide new fluid fast enough, the
pressure will drop sufficiently low that the fluid ejected from the
printhead will either cease or the quality of the drop will diminish.
Conversely, if the flow of fluid into the reservoir from the back-pressure
regulator is too great, the ability of the back-pressure regulator to
stabilize sufficient back-pressure is affected when only low volumes of
fluid are ejected from the printhead. It is essential that the drop volume
of the fluid ejected from the printhead be consistent to achieve high
print quality. Achieving consistent drop volume requires that the
back-pressure range be controlled to an ever finer levels.
Another requirement for an improved back-pressure regulation is to
accommodate air that is built up over time within the print cartridge
reservoir. This air is introduced by diffusion through system components
or tubing, at fluid interconnects in the pressurized system, or from air
that has been released from the fluid itself through out-gassing. A
pressurized system can introduce air either during refilling or
replacement of the main fluid source. This air can also be released from
the fluid either during changes in temperature or atmospheric pressure
changes due to weather or elevation. Size constraints on the print
cartridge often provide a limited capacity for warehousing air within a
reservoir of fluid within the print cartridge. If the amount of air within
the reservoir of the print cartridge becomes too large, either the print
cartridge will not be able to supply a sufficient amount of ink during
high speed, high density printing, or it may not allow the back-pressure
regulator to operate properly. In addition, large amounts of air will
respond to changes in atmospheric pressure and/or temperature. These
responses may cause the printhead to drool (the air expanding) or to
deprime (the air contracting). Depriming occurs when the ink within the
printhead is drawn back into the reservoir. Therefore air within the
reservoir causes the printing system to have a reduction in visual quality
or to simply fail to work properly.
SUMMARY
A print cartridge is used in a printing system in which there is a
requirement to provide at least two distinct rates of ink usage
corresponding to at least two different types of printing done with the
printing system. The print cartridge includes an ink replenishment path
which selectively provides at least two flow rates into the print
cartridge. The print cartridge also includes a controller which selects
one of the at least two flow rates into the print cartridge based on which
type of printing is being performed by the printing system.
The print cartridge can further include a removal path which is operated by
the controller in response to gauge pressure sensed within the print
cartridge. This removal path allows for the extraction of excess air and
ink in order to allow the gauge pressure within the print cartridge to be
regulated within a predetermined range that is suitable for the type of
printing being performed by the printing system.
One aspect of the print cartridge has a reservoir containing a quantity of
fluid. The print cartridge has a first valve defining a first fluid path
between a fluid source and the reservoir, and a second valve defining a
second fluid path between the fluid source and the reservoir, the second
fluid path being different from the first fluid path. The print cartridge
has a controller which is linked to each of the first and second valves.
The controller, in response to gauge pressure sensed in the reservoir,
modulates each of the first and second valves to provide fluid flow in the
first and second fluid paths, respectively.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a previously described back-pressure regulator
which uses multiple valves.
FIG. 2 is a block diagram of one embodiment of the back-pressure regulator
of the present invention which makes use of staged flows.
FIG. 3 is a block diagram of an alternative embodiment of the back-pressure
regulator of the present invention using air purge capability along with
the staged flows to further control the back-pressure of a print
cartridge.
FIG. 4 is a flow chart of a process of the present invention for providing
improved back-pressure regulation using the multiple valves illustrated in
FIG. 2 and FIG. 3.
FIG. 5A is a graph showing the operation of a previously described stop
valve versus the back-pressure in a print cartridge.
FIG. 5B is a graph showing the operation of a first valve used in the
embodiment of the invention versus the back-pressure in a print cartridge.
FIG. 5C is a graph showing the operation of a second valve used in the
embodiment of the invention versus the back-pressure in a print cartridge.
FIG. 5D is a graph showing the operation of a vacuum valve used in the
embodiment of the invention to effectuate air purge capability versus the
back-pressure in a print cartridge.
FIG. 5E is a graph showing the fluid flow into the print cartridge by
combining the effects of the first and second valve operation to create a
staged flow.
FIG. 6A is a partial cross-sectional drawing of one embodiment of the
invention using multiple valves to create a staged fluid flow.
FIG. 6B is a partial cross-sectional drawing of the embodiment of FIG. 6A
illustrating the first valve operation under normal conditions.
FIG. 6C is a partial cross-sectional drawing of the embodiment of FIG. 6A
illustrating the first and second valve operating under high output
conditions.
FIG. 7A is a partial cross-sectional drawing of a first alternative
embodiment of the invention in which air purge capability is provided.
FIG. 7B is a partial cross-sectional drawing of the embodiment of FIG. 7A
illustrating the vacuum valve opening due to the back-pressure approaching
atmospheric levels.
FIG. 7C is a partial cross-sectional drawing of the embodiment of FIG. 7A
illustrating the fluid valve operation under normal operation.
FIG. 8A is a partial cross-sectional drawing of a second alternative
embodiment of the invention combining the staged fluid flows and air purge
capability to provide improved back-pressure regulation.
FIG. 8B is a partial cross-sectional drawing of the embodiment of FIG. 8A
illustrating the vacuum valve opening due to the back-pressure approaching
atmospheric levels.
FIG. 8C is a partial cross-sectional drawing of the embodiment of FIG. 8A
illustrating the first fluid valve opening under normal operation.
FIG. 8D is a partial cross-sectional drawing of the embodiment of FIG. 8A
illustrating the first and second fluid valves operating under high output
conditions.
FIG. 9 is a partial cross-sectional drawing of a third alternative
embodiment of the invention in which the fluid source is integral to the
print cartridge.
FIG. 10 is a partial cross-sectional drawing of the embodiment of FIG. 9
illustrating how the print cartridge is capable of being recharged.
FIG. 11 is a partial cross-sectional drawing of a fourth alternative
embodiment of the invention in which the fluid source and vacuum chamber
are removable and replaceable.
FIG. 12 is an isometric view of a printing apparatus using at least one
embodiment of the invention.
DE
TAILED DESCRIPTION OF THE PREFERRED AND ALTERNATE EMBODIMENTS The invention
provides for tighter back-pressure regulation in a print cartridge. Print
cartridges can have several meanings depending on the type of printer they
are used in. A print cartridge for an off-axis printer is generally
smaller than a print cartridge for an on-axis printer. An off-axis printer
generally contains an ink source that is "off-axis", that is the ink
source is not placed within the axis used to move the print cartridge
across the recording medium. Since the ink source does not have to move
with the print cartridge, the print cartridge is able to print faster due
to its lower mass. An on-axis printer generally combines the ink source
within the print cartridge. While the print cartridge is typically larger
than an off-axis print cartridge, the user benefits by being able to
quickly replace an empty or defective print cartridge. The instant
invention is intended to provide tight back-pressure regulation for either
an off-axis or on-axis type print cartridge.
FIG. 1 illustrates a previously described approach to back-pressure
regulation using multiple valves in commonly assigned U.S. Pat. No.
5,719,609. In this approach a fluid source 20 provides a fluid under
pressure using pump 22 to a fluid outlet 24. The pump 22 is of
conventional construction and pressurizes the fluid to a supply gauge
pressure of about +30 inches of water to +90 inches of water. Note that
gauge pressure is used within the specification to describe the pressure
within a structure with respect to the pressure outside of the structure.
For instance, a gauge pressure of 0 (zero) inches of water is the level of
atmospheric pressure outside of the pump 22. The fluid outlet 24 is
fluidically coupled to a print cartridge 10 that includes a fluid inlet
26, an inlet reservoir 18, an optional stop valve 28, a regulator valve
30, a local reservoir 34, a pressure sensor 32, and a printhead 36. The
fluid outlet 24 interfaces with fluid inlet 26 to provide the pressurized
fluid to the print cartridge 10. A back-pressure regulator made up of
optional valve 28, regulator valve 30, and pressure sensor 32 controls the
pressure of the fluid in local reservoir 34 before it is supplied to
printhead 36. The pressurized fluid from fluid source 20 ensures that the
fluid reliably reaches the print cartridge 10 at high flow rates from the
printhead 36. However, if the fluid pressure within local reservoir 34
were not lowered below atmospheric pressure, the fluid would be forced out
of printhead 36 causing drooling. Therefore, it is important that the
back-pressure regulator control the pressure of the fluid in local
reservoir 34 such that it maintain a negative gauge pressure (relative to
atmospheric pressure external to the print cartridge 10) such as in an
exemplary range of -2 to -10 inches of water. When the printhead 36 expels
fluid, it must provide a force overcoming this back-pressure in the local
reservoir 34. When the fluid is expelled, it alters the back-pressure
value and the back pressure regulator must compensate for this. If the
back-pressure could be maintained in a tighter range than done with
conventional regulators, the amount of fluid ejected and its velocity
could be more accurately controlled thus allowing for better print quality
and faster printing.
The optional stop valve 28 provides a method of preventing the pressurized
fluid from fluid source 20 from entering the local reservoir 34 if
regulator valve 30 does not close completely. If regulator valve 30 does
not close completely, the pressure within local reservoir 34 increases
causing the optional stop valve to close when a set value is reached. Also
the pressure can rise if the quantity of air contained in the local
reservoir 34 becomes too large a portion of the volume of local reservoir
34, the optional stop valve will then close once the set pressure level is
reached to limit drooling from the printhead. The optional stop valve does
not, however, do anything to remove the excess air from local reservoir
34.
FIG. 2 illustrates a block diagram of an embodiment of a printing system
which includes pressure regulation techniques of the present invention.
The printing system contains a print cartridge 12 that has a back-pressure
regulator made up of a first regulator valve 40, a second regulator valve
38, and a pressure sensor 32. This back-pressure regulator allows fluid
from fluid inlet 26 to enter the local reservoir 34 while maintaining the
back-pressure in local reservoir 34 within a predetermined range.
The back-pressure regulator provides this improved back-pressure regulation
by providing aggregated flows of fluid in stages, that is, multiple fluid
flow through different fluid flow paths from the fluid inlet 26 and inlet
reservoir 18 to the local reservoir 34. Each fluid flow path has a
regulator, such as a valve, associated with the respective fluid flow path
for controlling the fluid flow between the fluid inlet 26 and the local
reservoir 34. This staged fluid flow is provided by having pressure sensor
32, when it detects a first pressure threshold, to open the first
regulator valve 40. If the fluid exiting printhead 36 exceeds the fluid
entering through the first regulator valve 40, the back-pressure in local
reservoir 34 will become more negative. When pressure sensor 32 detects
that the back-pressure has reached a second pressure threshold, it opens
the second regulator valve 38 which provides additional fluid to enter
local reservoir 34. If the combined fluid flows from first regulator valve
40 and second regulator valve 38 are greater than the fluid exiting
printhead 36, then the back-pressure in local reservoir 34 will become
more positive. When the pressure sensor 32 detects that the back-pressure
is greater than the second pressure threshold, then it closes the second
regulator valve 38. If the printhead 36 reduces the amount of exiting
fluid such that the back-pressure in local reservoir 34 is detected by the
pressure sensor 32 as greater than the first pressure threshold, then the
first regulator valve is closed to maintain the back-pressure in local
reservoir 34, which prevents drooling of fluid from printhead 36. This
back-pressure regulator provides better regulation of the pressure within
the local reservoir 34 which provides consistent drop volume of fluid
ejected from the printhead 36 resulting in higher print quality.
FIG. 3 illustrates another block diagram of an embodiment of a printing
system using one technique of back-pressure regulation in the invention in
which the back-pressure regulator in print cartridge 14 further includes a
vacuum regulator valve 42 controlled by pressure sensor 32. This vacuum
regulator valve 42 is disposed between the local reservoir 34 and a vacuum
reservoir 44, which is connected to a vacuum inlet 46. If air is contained
in local reservoir 34, the back-pressure in local reservoir 34 can become
more positive due to fluctuations in ambient pressure or temperature, even
if the first regulator valve 40 and the second regulator valve 38 are
closed. If pressure sensor 32 detects that the back-pressure in local
reservoir 34 approaches a third pressure threshold, then vacuum valve 42
opens, and air, and possibly some fluid, from local reservoir 34 is drawn
into vacuum reservoir 44. This action actively causes the back-pressure in
local reservoir 34 to become more negative until the pressure sensor 32
detects that the back-pressure is below the third pressure threshold
causing vacuum valve 42 to close. A continuous vacuum can be created in
vacuum reservoir 44 by having a vacuum source connected to vacuum inlet
46, or it can be created intermittently by periodically evacuating vacuum
reservoir 44. By having the vacuum regulator valve 42 actively respond and
correct for pressure changes, the first regulator valve 40 can be
eliminated and back-pressure stability at low fluid flows through the
printhead 36 can still be maintained.
FIG. 4 illustrates an exemplary process for controlling the back-pressure
within the local reservoir 34 of the print cartridge block diagram of FIG.
3. In this example, a desired predetermined back-pressure range from -2 to
-6 inches of water, is assumed. This example also assumes that when the
back-pressure reaches a pressure of -1 inch of water that enough air has
accumulated in the local reservoir 34 such that it needs to be evacuated
to prevent drooling of fluid from the printhead 36. The process would
start by using the pressure sensor 32 to sense the back-pressure in block
50. In decision block 51, the back-pressure is checked to determine if it
is greater than -1 inch of water. If so, then the vacuum valve is
activated in block 54 to allow the air accumulated in the local reservoir
to be drawn into the vacuum reservoir, thus lowering the back-pressure.
The process then returns to block 50. In decision block 51, if the
back-pressure is less than -1 inch of water, then in block 52 the vacuum
valve 42 is deactivated to prevent any further air or fluid from reaching
the vacuum reservoir 44. In block 56, the pressure is checked to determine
if it is less than -2 inches of water. If it is not then the first
regulator valve 38 is deactivated in block 58 to prevent fluid from the
fluid inlet 26 from entering the local reservoir and increasing the
pressure. The process would then return to block 50. In block 56, if the
pressure is less than -2 inches of water, then in block 60, the first
regulator valve 40 is activated to allow fluid to flow into the local
reservoir 34 from fluid inlet 26 thus raising the pressure within local
reservoir 34. If the printhead is expelling fluid at a volumetric rate
greater than the fluid entering the first regulator valve 40, however, the
amount of fluid within local reservoir 34 will decrease, and the pressure
inside it will continue to drop. In decision block 62, the pressure is
checked to determine if the maximum negative pressure of-6 inches of water
is reached. If it has not been reached, then the second regulator valve 38
is deactivated in block 64 and the process returns to block 50.
If the maximum negative pressure of -6 inches of water has been reached,
then in block 66, the second regulator valve 38 is activated to increase
the flow of fluid into the local reservoir 34. The process then returns to
sensing the back-pressure in block 50. By performing these steps, the
back-pressure within local reservoir 34 can be maintained within an
exemplary tight range of -2 to -6 inches of water. If the air released
from the fluid in local reservoir 34 over time causes the minimum negative
pressure to increase from -2 to -1 inches of water, then the vacuum valve
will be activated to expel the air inside local reservoir 34 so as to
prevent the back-pressure from getting higher than -1 inches of water.
This pressure value of -1 inches of water will prevent the drooling of
fluid from the printhead 36.
FIG. 5A is a chart illustrating the operation of the previously described
stop valve versus the back-pressure of local reservoir 34 in a previously
described print cartridge as illustrated in the block diagram of FIG. 1.
In this instance, when the back-pressure rises to between 0 and -1 inch of
water, the stop valve is closed, thus preventing any flow of fluid into
the local reservoir 34 and minimizing drooling of ink from the print
cartridge.
FIG. 5B is an exemplary chart of the operation of the vacuum regulator
valve 42 of FIG. 3 versus the back-pressure sensed by the pressure sensor
32. In this example, when the pressure within the local reservoir 34 rises
between -1 and 0 inches of water, the vacuum regulator valve 42 is
activated to evacuate the air from the local reservoir 34. By evacuating
the air, the pressure within the local reservoir 34 will become more
negative causing the vacuum regulator valve 42 to be deactivated. Since
the air has been evacuated from the local reservoir 34, the evacuated
volume within the local reservoir 34 can eventually be replaced with
fluid, allowing the back-pressure regulator to continue to operate.
FIGS. 5C-5E are exemplary charts demonstrating the stage fluid flow
operation of the invention shown in FIG. 3. In FIG. 5C, the operation of
the first regulator valve 40 is compared to the back-pressure sensed by
the pressure sensor 32. If the pressure sensed is less than -2 inches of
water, the first regulator valve 40 is activated. The amount of fluid is
modulated from -2 inches of water to -4 inches of water at which the first
regulator valve 40 is fully activated. If the pressure sensed is greater
than -2 inches of water, the first regulator valve 40 is deactivated. In
FIG. 5D, the operation of the second regulator valve 38 is compared to the
back-pressure sensed by the pressure sensor 32. If the pressure sensed is
less than -4 inches of water, then the second regulator valve 38 is
deactivate, else if the pressure sensed is more than -4 inches of water
the second regulator valve 38 is activated. The fluid flow through the
second regulator valve 38 is modulated until the pressure sensed is -6
inches of water at which the second regulator valve 38 is fully opened.
Combining the operation of the first regulator valve 40 with the operation
of the second regulator valve 38, provides the chart illustrated in FIG.
5E. This chart shows the fluid flow into local reservoir 34 versus the
back-pressure sensed by pressure sensor 32. In this example, no fluid
flows from 0 to -2 inches of water. Once the first regulator valve 40
opens, a first flow enters the local reservoir 34 and increases with a
slope1 up to a level of Y1. This first fluid flow continues until the
back-pressure reaches -4 inches of water. At that time the second
regulator valve 38 activates increasing the fluid flow into the local
reservoir 34 to a level Y2 with an increase of slope2.
Depending on the needs of the printing system, the fluid flow from the
first regulator valve 40 may be greater, equal, or less than the
additional fluid flow from the second regulator valve 38. What is
important over other pressure regulated printheads, such as that
illustrated by FIG. 1, is that the flow of fluid into the printhead is
provided in multiple stages of fluid flow, the multiple stages of fluid
flow being dependent on the back-pressure sensed within the printhead.
Slope1 is designed to be preferably shallow to allow for low ink flow
rates typically required in printing text information. Slope2 is
preferably steeper than slope1 to allow for high ink flow rates typically
required in printing graphic information. Those skilled in the art will
appreciate that the valve orifice and valve geometry can be modified to
yield different slopes and thus different fluid flow characteristics and
still meet the spirit and scope of the invention. Using the above
technique, exemplary examples of physical embodiments of the invention are
described and illustrated with respect to FIGS. 6A-12.
FIG. 6A is a partial cross-sectional diagram of one embodiment of the
invention derived from the block diagram shown in FIG. 2. In this
embodiment of a print cartridge 200, two valves are used to provide a
staged flow of fluid into the local reservoir 96. The print cartridge 200
is made up of a crown 94, a base 92, and a back-pressure regulator 100.
The base 92 has a local reservoir 96, a fluid screen 98 and a printhead
90. The screen 98 filters out unwanted particles from the fluid to prevent
the printhead 90 from clogging. The crown 94 has a fluid inlet 70, an
inlet reservoir 72, an orifice of first regulator valve 74, an orifice of
second regulator valve 76, and back-pressure regulator 100. Back-pressure
regulator 100 is made up of an air bag 88 with an inside that is vented to
the atmosphere outside of print cartridge 200 through air vent 80 and air
plug 78. Air bag 88 is allowed to expand or contract in response to the
pressure within print cartridge 200. As air bag 88 expands, force is
exerted on a first moment arm 102 and a second moment arm 104. The
combination of the air bag 88, spring 82, and the moment arms act to form
the pressure sensor 32 previously described. The air bag 88 is light
weight, flexible, deformable, and non-elastic. The air bag 88 is
preferably fabricated from a thin high barrier based film into four
adjacent pockets to increase the contact of the air bag 88 with the moment
arms to create a force. This force is counter balanced with a force
exerted by spring 82 which is connected to the first moment arm 102 and
the second moment arm 104. To apply different force levels on the moment
arms, each moment arm has a moment contact area at unequal distances from
pivot points on the respective moment arm. The first moment arm 102 has a
first moment contact area 106 which is as far distant from the first pivot
point 84 as possible. The second moment arm 104 has a second moment
contact area 108 closer to the second pivot point 86 than the first moment
contact area 106 is to the first pivot point 84. The first moment arm 102
forms a valve seat of the first regulator valve 74. The second moment arm
forms a valve seat of the second regulator valve 76. The valve seat is
preferably formed from a silicon elastomer.
The print cartridge 200 of FIG. 6A is functionally equivalent to the print
cartridge 14 shown in FIG. 2. The air vent 80, air plug 78, air bag 88,
spring 82, first moment contact area 106, and second moment contact area
104 are functionally equivalent to the pressure sensor 32 of FIG. 2. The
inlet reservoir 72 is functionally equivalent to the inlet reservoir 18
shown in FIG. 2. The local reservoir 96 is functionally equivalent to the
local reservoir 34 shown in FIG. 2. The first regulator valve 74,
controlled by the pressure sensor through the use of first moment arm 102
and first pivot point 84, is functionally equivalent to the first
regulator valve 40 of FIG. 2. The second regulator valve 76, controlled by
the pressure sensor through the use of second moment arm 104 and second
pivot point 86, is functionally equivalent to the second regulator valve
38 of FIG. 2. The printhead 90 functionally equivalent to the printhead 36
shown in FIG. 2.
FIG. 6B illustrates the operation of this embodiment of the invention when
the back-pressure in local reservoir 96 drops to a first predetermined
level. As the pressure in local reservoir 96 drops, the air bag 88 expands
since the inside of the air bag 88 is at atmospheric pressure and the
outside of the air bag 88 is at the pressure of the local reservoir 96.
The expanding air bag 88 presses on first moment contact area 106, causing
first moment arm 102 to rotate around first pivot point 84. This rotation
causes first regulator valve 74 to activate and open, thus allowing fluid
from inlet reservoir 72 to flow into the local reservoir 96. As first
moment arm 102 rotates, additional force is exerted on spring 82 which
tends to keep second moment arm 104 from rotating. However, as the
pressure in local reservoir 96 is further reduced, the air bag 88
continues to expand and create a larger force on first moment contact area
106 and second moment contact area 108. When a second predetermined
back-pressure level has been reached and moment arm 102 hits the wall of
the pen body, as shown in FIG. 6C, the second moment arm 104 rotates
around second pivot point 86, activating and opening the second regulator
valve 76. When this second regulator valve 76 opens, the first regulator
valve 74 remains open, and both regulator valves allow fluid to flow into
local reservoir 96.
FIG. 7A is a partial cross-sectional drawing of a first alternative
embodiment of the invention implementing a portion of the block diagram
shown in FIG. 3 in which a vacuum valve 124 (vacuum valve 24 in FIG. 3)
couples the local reservoir 96 to a vacuum reservoir 120 (vacuum reservoir
44 in FIG. 3). The print cartridge 202 is made up of a base 92 and crown
94. The base 92 has a portion of the vacuum reservoir 120, a screen 98,
local reservoir 96 and printhead 90. The crown 94 includes a vacuum inlet
122 (vacuum inlet 46 in FIG. 3), fluid inlet 70 coupled to inlet reservoir
72, an orifice of vacuum valve 124, an orifice of a first regulator valve
74 and a back-pressure regulator 100. The back-pressure regulator has a
first moment arm 102 with a first moment contact area 106 and a second
moment arm 104 with a second moment contact area 108. The moment arms
pivot around a first pivot point 84 and a second pivot point 86. The
moment arms move about the pivot points due to the force exerted by air
bag 88 and spring 82. The inside of air bag 88 is vented to the ambient
atmosphere through air vent 80 and air plug 78. When the pressure within
the local reservoir 96 decreases, the air bag expands, applying force on
the first moment contact area 106 and the second moment contact area 108.
Due to the location of the moment contact areas on their respective moment
arms, the amount of rotational force delivered to the pivot points for
each moment arm is different. When the pressure within the local reservoir
approaches the ambient atmospheric pressure outside of the print cartridge
202, the air bag 88 essentially deflates and the moment arms are rotated
about their respective pivot points by the force exerted by spring 82.
As illustrated in FIG. 7B, in this first alternative embodiment, the first
moment arm 102 has its pivot point 84 located such that the first moment
arm 102 activates and opens vacuum valve 124 when the air bag 88 is
deflated. When vacuum valve 124 is opened, any air, and possibly some
fluid, within local reservoir 96 is expelled into vacuum reservoir 120.
This action has the effect of lowering the pressure within the local
reservoir 96, thus inflating air bag 88 until vacuum valve 124 is
deactivated and closed essentially by the reactive movement of first
moment arm 102.
FIG. 7C illustrates the operation of the first alternative embodiment of
print cartridge 202 in which the fluid expelled by printhead 90 causes the
pressure within local reservoir 96 to drop, thus causing air bag 88 to
continue expanding and applying force on the moment arms. Since the first
moment arm 102 is prevented from further rotation due to the closure of
vacuum valve 124, the second moment arm 104 rotates around second pivot
point 86, activating and opening first regulator valve 74. When first
regulator valve 74 is opened, fluid is allowed into local reservoir 96
from inlet reservoir 72. As the fluid fills the volumetric space of local
reservoir 96, the pressure within the local reservoir 96 will increase,
causing the air bag 88 to deflate until first regulator valve 74 is
deactivated and closed. Thus, depending on the designed opening and
closing points of first regulator valve 74 and vacuum valve 124, a
predetermined specified back-pressure range is controllable within local
reservoir 96.
FIG. 8A is a partial cross-sectional drawing of a second alternative
embodiment of the invention which utilizes the print cartridge block
diagram shown in of FIG. 3. In this example, three valves are used to
control the pressure within local reservoir 96. The valve seat for first
regulator valve 74 is attached to first moment arm 102 using a first valve
spring 128. The valve seat for vacuum valve 124 is also attached to first
moment arm 102 using a second valve spring 126. The vacuum valve 124 and
the first regulator valve 74 are on opposite sides of the first pivot
point 84. The second regulator valve 76 is attached to the second moment
arm 104. The second alternative embodiment of print cartridge 204 has a
base 92 and a crown 94. The base 92 has local reservoir 96, a fluid screen
98, a portion of the vacuum reservoir 120 and the printhead 90. The crown
94 contains the vacuum inlet 122, the fluid inlet 70 coupled to inlet
reservoir 72, portions of the three valves, and the back-pressure
regulator 100. The back-pressure regulator 100 is again made up of a first
moment arm 102 having a first moment contact area 106, a second moment arm
104 having a second moment contact area 108, air bag 88, and spring 82.
The inside of air bag 88 is coupled to the ambient atmospheric pressure
through air vent 80 and air plug 78. The spring 82 is attached to the
moment arms and acts as a counterbalancing force exerted on the moment
arms from air bag 88. As the pressure within the local reservoir
decreases, air bag 88 expands, causing the moment arms to move about their
respective pivot points. When the pressure within local reservoir 96
approaches atmospheric pressure outside of print cartridge 204, the air
bag 88 deflates, allowing the spring 82 to draw the two moment arms
together.
FIG. 8B illustrates the operation of the second alternative embodiment when
the pressure within the local reservoir 96 approaches the outside
atmospheric pressure of print cartridge 204. The first valve spring 128 is
compressed to allow the first moment arm 102 to rotate due to the spring
82 force and the deflation of air bag 88. In this instance, any air within
the local reservoir 96 will be exhausted into the vacuum reservoir 120 and
thus lower the pressure within the local reservoir 96 until the vacuum
valve 124 deactivates and closes.
FIG. 8C illustrates the operation of the second alternative embodiment when
the pressure within the local reservoir 96 is reduced enough to cause air
bag 88 to expand and apply force on first moment arm 102. The second valve
spring 126 is compressed to allow the first moment arm to rotate and
activate first regulator valve 74 to open. When first regulator valve 74
is opened, fluid from inlet reservoir 72 is allowed to flow into the local
reservoir 96. As the fluid enters the local reservoir 96, the pressure
within the local reservoir 96 rises and first regulator valve 74 will be
deactivated and close.
FIG. 8D illustrates the operation of the second alternative embodiment when
the pressure within the local reservoir 96 is reduced due to a large
amount of fluid flowing through printhead 90. In this instance, the air
bag 88 expands causing both the first regulator valve 74 and the second
regulator valve 76 to be activated due to the force exerted by the air bag
88 on the moment arm contact areas. By opening both regulator valves, the
amount of fluid allowed to flow into the local reservoir 96 is increased
and can match the fluid output by printhead 90. As printhead 90 quits
ejecting fluid, the fluid entering the local reservoir 96 will fill the
vacant volumetric space of the local reservoir 96, thus increasing the
pressure within the local reservoir 96. This increased pressure causes the
second regulator valve 76 to be deactivated until closed and when
printhead 90 reduces its fluid output, eventually the first regulator
valve 74 will be deactivated and closed.
FIG. 9 illustrates a third alternative embodiment of the invention, using
the valve mechanism shown in FIG. 8A. The crown 94 of the print cartridge
206 contains a fluid source 132 with an optional refill inlet 130 and an
optional air vent 138. This print cartridge 206 allows for operation in
printing apparatus without having the need for separate fluid reservoirs.
This approach allows the user of a media printing apparatus to simply
replace or refill the print cartridge 206 when it becomes empty. Optional
refill inlet 130 allows the print cartridge 206 to be refilled with fluid
when needed. Optional air vent 138 allows the pressure within the fluid
source 132 to remain at external atmospheric pressure to ensure the
gravitational flow of fluid through the first regulator valve 74 and
second regulator valve 76.
The optional air vent 138 also provides a path for removal of internal air
if the print cartridge 206 is refilled with fluid. The operation of the
back-pressure regulator is as described above for FIGS. 8A-8D. The other
back-pressure regulator embodiments previously discussed can also be used
and still meet the spirit and scope of the invention.
FIG. 10 illustrates a method for refilling the third alternative embodiment
of the invention. A first syringe 134 is filled with replacement fluid and
inserted into refill inlet 130. The plunger of first syringe 134 is then
pressed to force the replacement fluid within the first syringe 134 into
the fluid reservoir 132. As the fluid enters fluid reservoir 132, any air
within the reservoir is expelled through the optional air vent 138. A
second syringe 136, which may be the first syringe 134, is placed in the
vacuum inlet 122. The plunger of the second syringe 136 is then withdrawn
from the second syringe 136 to evacuate any air that is in vacuum
reservoir 120, thus creating a negative pressure within the vacuum
reservoir 120.
FIG. 11 illustrates a fourth alternative embodiment of the invention in
which a print cartridge 208, implementing the back-pressure regulator 100
shown in FIG. 8A, allows for removal and replacement of a fluid cartridge
140. The print cartridge 208 has a crown 94 and base 92. The base 92 is as
described for the base shown in FIG. 8A. The crown 94 for this embodiment
is made up of an inlet reservoir 72, vacuum reservoir 120, and
back-pressure regulator 100. The back-pressure regulator can be any of the
described embodiments and still meet the spirit and scope of the
invention. The crown 94 also has snaps 150, a fluid needle 152, a fluid
seal 154, a vacuum needle 156, and a vacuum seal 158. The fluid needle 152
is a hollow needle of conventional construction. The fluid seal 154 covers
an opening in the fluid needle 152, and the vacuum seal covers an opening
in the vacuum needle 156 when the fluid cartridge 140 is removed from the
print cartridge 208. The seals are mounted on springs to allow for their
withdrawal from the needle openings when a fluid cartridge 140 is inserted
into the print cartridge 208. The fluid cartridge 140 has a fluid source
132, a vacuum source 142, snap receivers 160, a vacuum inlet 148, and a
fluid inlet 146. The vacuum inlet 148 and fluid inlet 146 are preferably
implemented as rubber septums of conventional construction with metal caps
and a housing fabricated of a liquid crystal polymer or other suitable
material. Snaps 150 attach to snap receivers 160 of the fluid cartridge
160 when connected to the print cartridge 208. The vacuum inlet 148 mates
to vacuum needle 156 and vacuum seal 158 of the print cartridge 208. The
fluid inlet 146 mates to the fluid needle 152 and the fluid seal 154 of
the print cartridge 208. When a fluid cartridge 140 is empty, the user can
disconnect the empty fluid cartridge 140 by using snaps 150 and
disengaging the fluid cartridge inlets from the needles of the print
cartridge 208. The empty fluid cartridge 140 can either be
refilled/recharged or replaced with a new fluid cartridge 140. The user
would insert the new fluid cartridge 140 onto the needles of the print
cartridge 208 and lock the fluid cartridge 140 in place with the snaps 150
and snap receivers 160. An air channel (not shown) is engraved into crown
94 or fluid cartridge 140 to allow air to vent to the inside of air bag 88
through air plug 78.
FIG. 12 is an isometric drawing, partially shown opened, illustrating a
media printing apparatus 180 such as a printer that contains at least one
embodiment of the invention. Media printing apparatus 180 is made up of a
media tray 170, a media feed mechanism 164, fluid supplies 172, and
printheads 200.
The invention allows for high flow rates of fluid into a print cartridge
having a printhead while still maintaining back-pressure stability at low
flow rates from the printhead. This capability allows for both high speed
and high quality printing such as that required for graphic imaging. This
capability is achieved by providing staged flows of fluid into the print
cartridge reservoir. In addition, the invention allows for tighter
back-pressure control and stability by providing a method and apparatus to
evacuate air that accumulates in the reservoir of the print cartridge.
This capability allows for a long life print cartridge which increases
reliability and lowers the consumer's operating costs.
Although specific embodiments of the invention have been described and
illustrated, the invention is not limited to the specific forms or
arrangements of parts so described and illustrated. For example, although
the specific embodiments described herein are directed to thermal ink-jet
printheads, the invention can be used with both piezoelectric and
continuous flow printheads. In addition, although a staged fluid flow
back-pressure regulator was illustrated and described as implemented by
mechanical means, the staged fluid flow back-pressure regulator can be
implemented with electrical and electronic sensors and valves controlled
by logic or computer circuits and still meet the spirit and scope of the
invention.
Further embodiments of the invention have been contemplated. One embodiment
has the print cartridge having a plurality of regulator valves that are
all in parallel which allow for variable flow rates that are required for
certain types of printing other than text or graphic. For example,
printing bar code labels continuously would require brief periods of
variable flows of ink mixed with brief periods of no ink printing. The
appropriate number of valves are opened corresponding to the level of ink
required to produce the width of the instantly printed bar. By being able
to adjust the flow of ink into the print cartridge based on the flow of
ink out of the printhead, tighter back pressure regulation occurs. This
technique then lends itself to allowing for dense and highly accurate bar
code printing.
To accommodate very high quality printing, the weight of an ejected drop of
ink is decreased. This reduction in drop weight means that any variation
in the amount of ejected ink caused by the back-pressure regulation
creates a larger percentage variation in drop weight during printing than
if the ejected drops had a larger weight. Therefore, the instant invention
provides for just such a tighter back-pressure regulation range required
to accommodate ever finer droplets of ink. The invention allows for an
even tighter range of back-pressure regulation than that which is
described in the exemplary embodiments.
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